Jigsaw with drive of scotch yoke type



April 2l, 1953 l JIGsAw WITH Filed March 22, 1947 B. W. HULFISH.

DRIVE OF SCOTCH YOKE TYPE 6 Sheets-Sheet l April 21,1953 B. w. HULFlsH`2,535,651

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B w HuLFlsl-l A i J-IGSAW WITH DRIVE OF SCOTCH YOKE TYPE Filed March 22,1947 Ilrr April 2.1, 1953 April 21, 1953 6 Sheets-Sheet 6 Filed March22, 1947' ,ZzUe/"f arf Patented Apr. 2l, 1,953

JIVGSAW WITH DRIVE OF SCOTCH YOKE TYPE Buford W. Hulfsh, Chicago, Ill.,assignor to Birtman Electric Company, a corporation of IllinoisApplication March 22, 1947, Serial No. 736,462

(Cl. 143-73) Y i 6 Claims.

. 1 Thisfinvention relates to a jig or scroll saw, and particularly tosuch a saw having improved means lfor reciprocating the saw vblade andpreventing the blade from turning about its Ylongitudinal axis.

In jig saw construction, it is necessary that the saw blade bereciprocated longitudinally in substantially ja straight line. Variousmeans have been proposed for obtainingthis straight line reciprocation,but these have often been cumbersomev and erratic in operation. With thestructure of the present invention, a motor is provided with thel motordriving a rotatable member and the rotatable member operating thereciprocating mechanism and preventing turning of the recipr'ocatingmechanism. The structure for maintaining the reciprocation is simple inconstruction and requires very little or no attention.

The invention will rbe described as related to the embodiment shown intheY accompanying drawings. VOf the drawings, Fig. 1 is a side elevationof a jig saw embodying the invention,

with portions broken away for clarity of illustration; Fig. 2 is a topplan view of the saw of Fig. 1'; Fig.3 is a horizontal section takenalong line V3-3of Fig-1; Fig. 4 is a vertical section taken along-line4-'4 of Fig. 3; Fig. 5 is a vertical section taken along line 5-5 ofFig. 4; Fig. 6 is a sectionrtaken alongl line 6-6 of Fig. 4; Fig. 7 is asectionztaken along line 1--1 of Fig. 4; Fig. Sis a section taken alongline 8-8 of Fig. 4; Fig. 9 isa section taken along line 9-9 of Fig. 4;Fig. 10-k is a section taken along line lll-I0 of Fig. 7; Fig,11 is asection taken along line I I-II of Fig. 10; Fig. 12 is a verticalsection taken sub-A stantially through the center of the structure towhich the upper end of the saw blade is attached; Fig. -13 is a sectiontaken along line l3l3 of Fig.` 12; and Fig. 14 is a section taken alongvline I'4-I4 of Fig. 12.

The jig saw shown in the accompanying drawings comprises a base adaptedto rest on a table or other support 2 I, a base housing 22 supported onthe base 20, a lower arm 23 extending fromthe base housing in anupwardly inclined direction, an upper arm 24 arranged substantiallyhorizontal and 'attached to the extended end of the llower arm 23 by avertical portion 25, a work support table 26 mounted above the basehousing 22 and adapted to support a board 21701' the like for beingsawed, and a saw blade 28 arranged substantially vertically andextending through a hole 29 provided in the work support table 26. g

In Figs. 1 and 12, the saw blade 28 is shown in its Luppermost raisedposition. In Figs. 4 and 1.5.7the'blade is shown-in its-loweredposition.

The work support table 26 through which the saw blade 28 extends isprovided with two downwardly extending spaced apart arcuate members 30on its lower` surface with these two members being arrangedsubstantially parallel to each other and bolted to the bottom of thetable. Each of the arcuate members 30 has an inwardly extending arcuateraised portion 30a on its inner surface. The top surface of base housing22 is provided with upwardly extending members 3l arranged substantiallyparallel to each other and having inwardly sloping sides 32. Eachupwardly extending member 3| is arranged adjacent an arcuate member 38and is provided with an arcuate groove 3| a which holds a raised portion38a. Each arcuate member 3D is provided with an arcuate slot 33 and abolt 34 is provided in each groove with each bolt having a head 34a anda threaded end 34h engaging similarly shaped threads in the upwardlyextending member 3l. With this construction, the table 2B may be turnedeither backward or forward to any angle desired and held in position bytightening the bolts 34.

The hole 29 provided in the work support table 26 and through whichthesaw blade 28 extendsV is provided with a top countersunk portion 29aextending below the top-surface of the table.

The bottom end of the saw blade 28 is removably attached `by means of asmall screw 35 to a bolt 36 having an enlarged head portion 36a the sawblade 28, the bottom of the stem is at-r tached to a transverse hollowportion 39 having a circular cross section and arranged substantiallyatright angles to the stem 31. The hollow portion 39 is provided with anelongated opening 40 in the form of a slot in one wall thereof. The

edges of the slot are cut away as at40a so that the hollow portion 39will not interfere with the end of the axle 42. The hollow portion 39 isprovided with two at faces 40h located between the ends of the slot andthe ends of the hollow portion 39. Both flat faces are in a single planeandv in continuous contact with the face of a heavy gear wheel 4|,thereby preventing any turning of the stem 3.1 about its longitudinalaxis. The

The stem 31 is slidably heldV heavy gear wheel 4I is mounted forrotation on an axle 42 extending from a transverse wall 43 within thehousing 22. The gear wheel 4l is arranged substantially parallel to thestern 31 and the guide member 38 and is made heavy or weighted so thatit serves as a fly wheel and a counterbalance. Located -within thehollow portion 39 is a slidable member 44 which is connected to the gearwheel 4| by a stud 45 having a circular cross section and held in asimilarly shaped pocket 46 in the gear wheel. The stud 45 has a portion45al also of circular cross section, but of larger diameter than theremainder of the stud, engaging a hole in the slidable member 44. Thestud 45 is free to rotate in the slidable member 44 and does not rotatein the pocket 46. Y

On the other side of the transverse wall 43 there is located a motor 41having a shaft 48 extending through the wall 43 and provided with apinion gear 49 engaging the gear teeth ofthe gear wheel 4|. The shafthas packing material 50 arranged around it. The transverse wall 43 isone wall of the inner housing surrounding the stem 31, guide member 39,hollow portion 39, gear wheel 4I, and pinion gear 49. This inner housingmay be kept partly filled with oil so as to provide lubrication to themoving parts of the reciprocating mechanism by means of the gear wheel4l, the lower portion of which extends below the oil level.

When the motor 41 is operated, it turns the gear wheel 4l and thisserves to slide the slidable member 44 back and forth in the transversehollow portion 39, and atthe same time prevents any turning of the stem31 about its longitudinal axis. This movement causes reciprocation ofthe stem 31 and thus of the blade 28. The elongated opening 40 isslightly longer than the diameter of the circle described by the stud 45during its movement. When the stud 45, the axle 42, and the stem 31 arein a single plane, the stud 45 will be located at substantially thecenter of the elongated opening 48.

The motor 41 is provided with four extending equally spaced ears 52,vall having base portions lying in` substantially a single plane, and themotor is fastened to the transverse wall 43 by bolts-53 extendingthrough the ears 52.

The top end of the saw blade 28 is held in the hollow interior ofacollar 54 by means ofa screw 55. The collar 54 is attached to thebottom of a hollow stem 56 of non-circular cross section. As shown, thestem is square. The top end of the stem extends up inside alsubstantially cylindrical housing 51 that is mounted in ahole 58 at theend of the upper arm 24. The top end of the stem 55 is attached to amember 59extending across the inside of the housing 51 and movabletherein. The member 59 is constructed of a packing material 68 heldbetween two parallel plates 6l. The packing material 68 serves to form aseal with the inner surface of thehousing 51 and the member 59,therefore, acts as a piston. The hollow interior of the stem 55communicates with the portion of the housing 51 above Vthe pistonthroughk a hollow threaded plug 52 extending through the piston member59; The upper end of the housing 51 is provided with a cap 63 having anopening 63a, thereinfor the entrance of air, Immediately below theVopening 63a there is located a iiutter valve 64 with the valve beingarranged to open as the piston member 59 moves down and close as thepiston-member 59 moves up.

f, The stem 58 extends through arguide member 65 extending across thebottom of the housing 51. The portion 65a of the guide member 65 whichengages the stern 56 is an oilite bearing or other self-lubricatingmaterial and is provided with a square hole through which the stemextends. The remainder of the guide member 55A is provided With threeequally spaced arcuate shaped openings 66 communicating with theinterior of the housing beneath the piston member 59. These openingsneed not be equally spaced. Extending between the top of the guidemember 65 and the bottom of the piston member 59 there is located acompression spring 61 with this spring beingY arranged around the stem56. The compression spring serves to urge the piston member 59 upwardly.

The housing 51 extends through the hole 58 in the upper arm 24 and alsothrough a hole 68 in a cap member 69 mounted on top of the outer end ofthe upper arm 24. This cap member is held'v in place by means of bolts1.0 extending.

through the outer end portion. 245 of the upper. arm 24. a block 1lwhich is a part of the cap member 69. This block 1l rests against amachined surface on the top ofthe arm 24V and has an arcu..

ate outer surface 12 against which the housing 51 is held. The housingis held in place by meansk of a strap 13 passing aroundthe housing 51,block 1l, and a movable nut 14. The nut 14l and strap 13 are held inplace by means of a bolt 15 having a threaded endY engaging similarlyshaped threads in the n'ut14. This bolt extends through one wall of thecap member' 69. By turning thebolt 15, the nut14 is moved towards thiswall to pull thestraptowardthewall and hold the'housing 51Y tightlyagainstthe arcuate surface 12. With this construction, the housing 51may be arranged in any desired position relative to the cap 69 and theupper-arm 24 and the housing becomes free by turning the bolt 15 tomovethe nut 14 away from this Wall. The forward end of the cap 69 extendsbeyond the end of the upper arm 24 to provide space for an eiectriclightbulb 1s. VThe bottom of the cap teY below the light bulb 16 is open sothat light may shine down on the work.

During the operation of the jig saw,1 a blast ofair is substantiallycontinuously*v applied tothe region adjacent the saw blade281to'maintain the kerf free of saw dust. When the piston member 59 ismoving downwardly, the air is forced out thespaced holes 66 that arelocated in the guide member 65. During this downward movement, thevalve. 64 opens to permit airtoV enter through the hole'63a intotherspace above the piston member 59. When the piston member 59 movesupwardly, the valve 64vcloses and thev entrapped air is forced down thehollow stem 56 through the collar 54and around the top end of the sawblade 28. This air stream is most effective as now the blade is movingupward and drawing saw dust up from the kerf.

In order to hold the saw blade 28 against the work 21 and alsovtoholdthe -work against.` the table 26, there is located adjacent the rearof thesaw blade a barl 11 arranged parallel to the saw blade andextending through the outer end of the upper arm 24 and the cap member69. This bar is held in place by means of a lock bolt 18 extendingthrough the side of the block 1| If desired the lock bolt 18 can extendthrough ahole in the upper arm 24 and carry aknob on its outer-end sothat .the .bolt can beA easily loosened andtightened. On the bottom of;the.

One of the bolts (notY shown) engages.

bar there is located a member 19 extending downwardly and toward the sawblade 28. Mounted on the end of this member there is locatedv arotatable wheel v8E! adapted to bear against `the back of the saw blade.The member 19 is held in place by a bolt 8| extending through a slot 11aat the bottom of the bar 11. The position of the member 19 may thus beregulated to'various distances above thetable 26. Mounted on the rearsurface of the member 19 there is located a downwardly extending foot 82having a bifurcated lower end adapted to straddle thesaw blade 28` and-bear against the work 21.

The apparatus for controlling the Speed of the motor comprises a plate83 mounted on the rear end of the extended motor shaft 48 just behindthe commutator 84, and adapted to be rotated by the plate, a secondplate S .mounted on the first plate 83 in spaced relationship thereto bymeans rthe plates 93 and 85 with each bell crank being rotatably mountedabout a fulcrum 90. Each bell crank 89 is arranged substantially betweenthe plates and has one leg 89a in contact with an arm 81 and the otherleg 89h lying principally between the plates. As the arm S1 is forcedoutwardly by centrifugal force, it bears against leg 89a and forces itoutwardly also. The bell crank 89 turns around the fulcrum 99 so thatthe other leg 89h is forced inwardly. Mounted between each pair ofadjacent ears 85h, there is located a second bell crank 9| rotatablymounted on a pin 92 extending between the ears. VThese bell cranks 9|are mounted at substantially right angles to the plate 83 and are soarranged that the free leg 89h of a bell crank 89 bears against theouter surface of a leg Sla of a bell crank 9 i. The legs 9|a extendtoward the plate S3. The other leg 9| bA of the bell crank 9|extendstowardthe shaft 98. With this construction, the legs Sib of thebell crankl the centrifugally responsive arms 81 are trans. mitted tooutward movement of the cap memberv 93. The faster the armature and theshaft 48.are revolved, the greater is the outward movement of the capmember 93. The speed of the motor can, therefore, be controlled byproviding contact arms opposite the end of the cap member 93 with theforce ofthe outward movement of the cap member serving to separate thearms when the speed reaches a predetermined maximum. This maximum isdependent upon the position of the contact arms relative to the adjacentend of the shaft 48. This entire construction is shown and described ingreater detail in the Charles H. Sparklin application Serial No.580,114, filed February 2 8, 1945, now Patent No. 2,532,345, issuedDecember 5, 1950.

control button |06 against the outer surface of In the presentconstruction, there are provided an inner contact arm 96 and an outercontact arm 91. The outer contact arm is made of two pieces of sheetmetal, or the like, connected together to form a yoke having an endportion 91a extending out of the motor housing 41a through a slot 4117provided therein. A pin 98 is provided extending between the base of thebifurcated portion ofthe yoke with this pin being held between outercontact arm 91, there is located an inwardly extending flange 91h upon.which is mounted an outwardly extending contact point 6U. A similarcontact point Illl is mounted on the free end of the inner Acontact arm96 with the two contact points being adapted to bear against each otherto close the electrical circuit to the motor. The outer contact arm 91is provided with a pair of outwardly extending side portions 91eextending toward the ,rear end of the motor housing 41a. These sideportions are connected by a bar 91d extending between them. Acompression spring |82 is arranged between the bar 91d and the centralportion 96a of the inner contact arm 96 opposite the free end of the capmember 93. This central portion 96a is provided with a button |03adapted to be contacted by the free end of the cap member 93. With thisconstruction the contact arms 96 and 91 may be rotated by means vof theend portion 91a of the outer contact arm 91 about the pin 98. Thispositions the contact arms relative to the outer end of the shaft 48. Asthe.

speed'of rotation of the motor increases, the cap member 93 bearsagainst the button |93 and forces the inner Contact arm 96 outwardlyagainst the compression spring |92. This causes separation of thecontact points |99 and IGI and breaks the electrical circuit to themotor. As the speed of the motor decreases, the compression spring |92forces the contact points back together so that the electrical circuitis again closed. As

can be seen, the speed of rotation depends upon the relative position ofthe contactarme, 96 and 91.

The end portion 91a of the outer contact arm 9'! is moved by means of abar member |04 having one end rotatably engaging the end portion 97d andthe other end extending through the front 22h of the base housing 22.This end of the bar member |94 extends'through a thickened portion 22oof the front of the-base housing and is slidably held therein. Mountedon a pin` extending through this thickened portion 22c is a controlbutton |86. The control button is held on the outer end of the pinbymeans of a set screw |91. The inner end of the pin |85 is providedwith a collar |99 that is held on the pin by a key E89. This collar |98isspaced from the inner surface of the thickened Iportion 22e and acompression spring H9 is arranged between the collar |99 and the innersurface of the thickened portion 22o. This spring serves to hold the thefront portion 22h of the base housing 22. The inner surface of theVcontrol button |96 is provided with a substantially circular cam sur- 1face against which the-outerv end of the bary assessor:

T [01'. bears. As the button |316" is turned,Y the cam surfacev I Hicauses the bar |011 to be moved longitudinally. Thismovement' of-'thebar turns the contact arms 9B1and 91 around. the. fulcrum pin 98 andpositions. the arms relative tothe rear end of the motor shaft 48'. Withthe parts at the positions shown in Figs. 4 and 10, the motor. willoperate at its slowestspeedi as the inner contact varm 9S is atits.nearest distance to the end of the shaft. 48. The bar |04, when moved toits farthest distance, moves contact' arm S1 relatively.: close totheend. of the shaft i8 thereby compressing the spring 102 and separatingthe contacts |001 and IBL to create an oli position..

Oneof the important features ofzthis invention is the mounting ofthemotor on the inner housing which. serves as the oil casing andconnecting the motor. directly through gearing to the meansforreciprocating theblade. This reduces: vibration to a minimum so that thejig saw runs quietly and smoothly. In most prior jig saws; vibration andnoise were problems primarily due tothe. inefficient means. employed intranslating rotary. motion to reciprocating. motion. Thus, prior jigsaws were often. jerky, erratic, and noisy. In the. present jig saw theweighted. over-size gear wheel I that serves'as a ily Wheel. also aids..in cuttingdown Vibration andi noise. The gear Wheel iii is provided withaout out section 41a. on itsfront face so located thatY the pin 45 isbetween this cut out section and the shafti42` Thisservesto at leastpartially compensate for the reciprocating. weight of the reciprocatingmechanism and reduce the magnitude of vibration. If desired a similarcut out section could be providedon the opposite face of the gear, or`on both faces.

The above features also. permit the employment of a speed control forthe motor as the motor runs smoothly and quietly at all speeds withoutslipping between the motor and the saw blade. In many prior jig sawsthemotor could notbe operated at low. speeds even if it were so desiredbecause the meansA for translating the n iotion were subject toslipping,

Other featuresof the invention are claimed in.

my copending applications Serial No. 741,973, filed'April'll?, 1947.,Serial No. 736,282, iiled March 2l, 1947, and' in the Charles H.Sparklin applicationSerial-No. 736,491, led March 22, 1947.

Having described my invention as related to the embodiment shown in theaccompanying drawings, it is my intention thatthe invention be notlimited by any of the details of description-unless otherwise speciedbutrather be construed broadly within its spirit and scope as set out inthe accompanying claims.

I claim.:

l. In a jig saw including a body portion, a table thereon and a sawblade extending through the table, a reciprocable member adapted to haveone end of the blade attached to one end of said member, the other endof said member having atransverse hollow portion thereon with anelongatedslot in one side wall thereof, saidrslot having the outer edgesrecessed and the transverse hollow portion having a pair of flatco-planar bearing surfaces each located at one end of the slot', guidemeans for said reciprocable member, a weighted rotatable member having ailat surface in sliding contact with said bearing surfacesthroughout therotation of said weighted member but with said recessed edges spacedfrom saidi flat surface to provide a spaced two-point contact. of thehollow` portion on the fiat surface, a; stud'rnemberV mountedfin saidweighted'.Y

member and extending through said slot into said-` transverse hollow.portion, av slidablemember in said hollow portion mounted on said studmember for sliding movement in the transverse portion on rotation of theweighted member to.

cause reciprocation of the reciprocable member, and, means for rotatingsaid weighted rotatable member about an axis spaced from the studmember, said elongated slot and its recessed edges being atr least aslong as the diameter of the' 3. In a jig saw including abody portion, atable thereon and a saw blade extending through the table, aclosedhousing withinsaid body portion, a reciprocable. member extending intothe housing adapted to have one end of the blade attached thereto, anelectric motor supported solely on an exterior surface of one. wall ofthe housing, gearing within the housing operatively connecting the innerend of the shaft and the reciprocable member for reciprocating saidmember and thus the blade on rotating said shaft, and a top plate memberforming a part of said housing and to which the remainder of the housingis attached and through which the reciprccable member extends, saidplate member extending beyond the side walls of the housing and havingthe edges of the extending Dart fastened to the marginal portionsurrounding an opening in said body portion so that the housing, thegearing, and; the

motor are `all supported from said plate memberthereon and a` saw bladeextending through the.

table, a reciprocable member adapted to have one end' of the bladeattached to one end thereof,v

means including a rotatable member operatively connected to the otherend of said reciprocable member for reciprocating the same in asubstantially straight line, and a three-point guide means aiding inrestraining. said` reciprocable member against substantial vibrationduring its reciprocation, said guide means including one guide portionembracing said reciprocablemember and a pair of spaced guide portions onopposite sides of the line of reciprocation and transverse, thereto, theguide portions being operatively attached to the reoiproc-able memberand. movable therewith, said pair of guide portions operating against aguide surface during operation of the device and being separatedA by arecessed part spaced from said guide surface.

6. In a jig saw including a body portion, atable thereon and a saw bladeextending through the table, a reciprocable member adapted to have oneend of the blade attached to one end thereof,

means including a rotatable member operatively 9 connected to the otherend of said reciprocable member for reciprocating said reciprocablemember in a substantially straight line, and a guide means embracing amajor portion of the length of the reciprocable member and extending toa point adjacent the point cf connection of the rotatable member to thereciprocable member to aid in restraining the reciprocable memberagainst substantial vibration during its reciprocation, said rotatablemember being provided with a flat side adjacent the reciprocable memberand the reciprocable member including a pair or" spaced co-planarbearing surfaces bearing against said flat side on opposite sides of theline of reciprooation and transverse thereto, the spaced bearingsurfaces being separated by a recessed part spaced from said iiat side,said spaced bearing surfaces and said guide means providing athree-point support serving to hold said reci-procabie member againstsubstantial rotation and vibration during its reciprocation.

BUFORD W. HULFISH.

References Cited in the file of this patent UNITED STATES PATENTS

